In such a connection arrangement which can be found in U.S. Pat. No. 3,845,748 the sealing surface of a pressure nipple which is provided at the end of the fuel line, that is introduced into the passage in the cylinder head, is pressed by means of a pressure transmission arrangement against a counterpart sealing surface on the nozzle holder, transmitting to the pressure nipple the force which is produced when a cap screw element is screwed into a female screwthread in the region of the inlet opening of the passage and tightened therein. That pressure transmission arrangement comprises two parts coaxially surrounding the fuel line, namely a pressure ring bearing directly against a pressure receiving surface on the pressure nipple and a pressing tube which in the assembled condition bridges over the distance between the pressure ring and the cap screw element.
As the possibility cannot be excluded that engine oil and/or fuel under very high pressure penetrates into the free spaces which, for reasons of allowing assembly, must be present between the external peripheral surface of the fuel line and the pressure transmission arrangement on the one hand, and the pressure transmission arrangement and the inside wall of the passage on the other hand, it is necessary to seal off the passage towards the outside of the cylinder head to prevent uncontrolled escape of those fluids and/or the penetration of moisture into the free spaces.
For that purpose the known cap screw element has a prolonged shaft which in the fully screwed-in and tightened condition projects outwardly from the inlet opening of the passage and there carries a male screwthread, on which is fitted a nut which by being rotated can be moved in the axial direction towards or away from a flat contact surface surrounding the inlet opening of the passage on the outside of the cylinder head. Arranged on the shaft of the cap screw element between the contact surface and the flat side of the nut, that is towards it, is an annular sealing disk which is pressed against the contact surface when the nut is tightened with the cap screw element being fully screwed in. As the inside diameter of the sealing disk must be markedly larger than the outside diameter of the shaft of the cap screw element so that, when the nut is tightened, the sealing disk can move over the male screwthread on the shaft towards the contact surface on the cylinder head, a further annular sealing element is required, which is arranged between the nut and the male screwthread on the shaft.
That known sealing arrangement suffers from a series of disadvantages. It requires preliminary assembly of the cap screw element, on to which firstly the nut must be screwed together with the interposed annular sealing element and then the sealing disk has to be pushed on before the unit formed in that way can be positioned on the fuel line. If then the fuel line is introduced into the passage in the cylinder head until the pressure nipple bears against the counterpart sealing surface of the nozzle holder and the cap screw element is tightened, in addition the nut carried on the shaft of the cap screw element has to be tightened to achieve a sealed closure for the inlet opening of the passage. In that situation the sealing element between the nut and the male screwthread on the shaft causes difficulty both in terms of initially screwing on the nut on to the shaft and also the definitive tightening thereof.